SML Striper Growth

[Deleted]

Hokie...the point of my post was it doesn't matter anyway.  I bet MWard could explain it real good.  He knows where I was going based on my questions.

You wanna give it a shot MWard?

[mwardncsu]

Uhmmm...... huh?

[Deleted]

Feb 10, 2014 22:47:04 GMT -5 BentRod said:

Feb 10, 2014 21:53:18 GMT -5 Yam said:

Good stuff Yam. I definitely respect you for all your research and inquires into the issue at hand. I think a few of us have been pouring over this for a couple years and we don't know up from down anymore.

"Don't make the same mistake twice." I think this is spot on. I know Dan has mentioned he saw the overpopulation occurring in the early 2000s and I honestly think he regrets not acting then, but how could he have known what would have happened? Just from speaking with him and listening to him over the last 4-5yrs, I can tell you he is not an overreactor, so the fact he thinks we need to act tells me something has him pretty concerned. I'm not sure that the Nov slot change two years ago wasn't the first step of action and we just didn't know it at the time. I have no idea the right course of action or even if we need to act at all, but after picking Dans brain and listening to him for the past 5 yrs, I trust his judgement. If I could sign on the dotted line to keep the fishery we have today, I'd do it. My fear is the fishery we have today will not be so in 5yrs if we keep on this same path.

Thanks Bentrod. I plan to live here the rest of my life and I finally found what I consider the perfect lake.



I feel that since I am not as close to the situation as all of you, that an outsider's objective inquiry would add value. Unfortunately, I have become too close to be unbiased myself.



This reminds me of that time when you finally find that perfect woman. And even though her butt may be a bit big to her, it is absolutely perfect for you. The next thing you know, your perfect woman goes on a diet and then starts injecting her lips and starts to look like one of those chicks on Real Housewives. She wanted to find a perfection that does not exist and ended up screwing herself up beyond repair. 

You see...I like my butts a bit on the chunky side!

I will say though that I don't see any statistical evidence that suggests a downtrend whatsoever.  I see a drop in growth after 03...but a downtrend?  Really??  I just don't see it!  Secondly, unless Dan did something creative, you shouldn't be comparing samples drawn from years with a slot limit with years minus a slot limit.  And to include 2013 data where the sampling techniques changed again?  Seems bad! And even worse (which causes my own bias), is my own experience that completely contradicts 2013 data.  On all 4 of my outings I caught at least one fish greater than 33" (9 total including a citation). The 2013 data set would suggest this to be extremely rare if not impossible even if I were an experienced SML fisherman.  And to top that all off, only 13 fish are over 9 years old in the 2013 data set compared to 41 in the 2011 data?  If this is representative, then my big fish were young.  Or...this could all be explained by: the lack of fish head data from the slot months is killing the samples.  I'm not sure about you guys, but I do most of my fishing during the slot months because this is when I catch my biggest fish. That's just me. Does the 00-02 data include year round data?

I have read one of Dan's papers and he (or at least his coauthor) is no slouch with stats, thus, there is something going on that I don't know about.  I just hope its not pressure and history that are driving him. It is possible that this slot is working great and that removing it could hurt this fishery once again. Thus there is risk. It is also possible that doing nothing is the right choice.  And it is also possible that increasing this slot won't do much.  And it is possible that increasing the slot will have an impact.  And it is possible that increasing this slot will have no impact and that mother nature and time was the real reason.  And....  See what I mean??

However, if you are acting because you are confident that there is a downtrend, then by all means you should act!  

PS  There is always bias in all data collection techniques.  The trick is to understand what you are studying and to create a standardized protocol for sampling.  Standardization at least allows bias to be consistent across samples.  And even harder yet, is when you spend countless hours doing all of this and your money source cuts your ability to implement correct procedures.

[BentRod]

My advice to all of you if you're passionate enough about it is to make yourself heard. Contact Dan, contact the DGIF. Ask questions, get informed, question what you're being told, research it, yell and scream, do whatever it takes to be heard by those that matter, and for God sakes will someone get Bigun a tissue!

[Deleted]

It's about time you noticed......it only took you 10 PAGES...........when I come back in my next life, i'm going to be reincarnated as a striper....and i'm goin to break your line.....everytime.    LOL!!!!

[BentRod]

Dan and the DGIF guys along with VaTech and I think maybe Lynchburg College later on were the first ones to really research these Copepods and learn how they affected Striper and bass populations..there was essentially no information on them before our Striper kill.

Looks like I was right (for once) about the Lynchburg College involvement...check this study out I just found...

lasi.lynchburg.edu/shahady_t/public/Achtheres.pdf

[mwardncsu]

Stripedyam - ok - I gotcha now........ yes, I've questioned if we have sufficient data on the larger fish that come from fish-heads to draw statistically significant conclusions - and if we are "self-selecting" some of the data by the fact that I expect most of the fish-heads come from fish caught in the summer - when the fish tend to be schooled up and we're catching, on average, smaller fish. The question is does this introduce a sample-bias - maybe. Although what is in question is not the # of fish over 30" or whatever, but their growth-date - size/age..... and any fish caught should provide valid data for this.... the question is if we have enough data for the larger fish..... maybe not on the ones up in the 35"+ size - but it does seem clear we have a growth trend change at the 25-28" range across age.....

[Deleted]

Feb 11, 2014 10:02:52 GMT -5 mwardncsu said:

Stripedyam - ok - I gotcha now........ yes, I've questioned if we have sufficient data on the larger fish that come from fish-heads to draw statistically significant conclusions - and if we are "self-selecting" some of the data by the fact that I expect most of the fish-heads come from fish caught in the summer - when the fish tend to be schooled up and we're catching, on average, smaller fish. The question is does this introduce a sample-bias - maybe. Although what is in question is not the # of fish over 30" or whatever, but their growth-date - size/age..... and any fish caught should provide valid data for this.... the question is if we have enough data for the larger fish..... maybe not on the ones up in the 35"+ size - but it does seem clear we have a growth trend change at the 25-28" range across age.....

Clear??  What if the >30 inch fish not present AT ALL in the 2013 data are all flourishing 6-8 year olds?  If this were the case, the age/growth data could change drastically. It is a very real possibility that the "puzzling notion" of "some of the fish are breaking through the growth barrier" is nothing more than a few smart fish being caught in the summer while all of their flourishing buddies roam the waters away from the chaos.


Could it be a sensible assumption that healthy fish do not need to school with the pack in the summer, thus they are not being caught? Or stated differently, could it be that older fish that are more stressed (who have been shown to actually lose weight in some cases over time) are more inclined to work the advantage of schools? I really have no clue on this. I do know that from my fishing experience, I tend to find the bigger fish above and below the schools.  

But I do have a clue on stats and if your sample does not represent the population then you are not allowed to make inferences.  However, you can make good management decisions if consistent sampling techniques show a notable change among the sample data you chose to study.  I just wish I could see a notable change during the 06-12 data period where the sampling techniques may have been consistent.  All I see is a major difference in growth rates before and after the kill.  And when one considers that we now have a parasite, a growth rate decline and a new equilibrium does not seem all that surprising to me.

[BentRod]

Yam where are you getting your data? There's a bunch of 30"+ fish in the 2013 data, some of which are in the range of 6-8yrs old and the numbers still look bad overall.

[CorneliaGale]

The paper from Lynchburg is some interesting reading, Looks like the fish are doomed until someway is found to get rid of the little buggers. I wonder it they secrete something that stops the fish from making white blood cells to help fight them. Also interesting there were more of them in winter fish than summer fish.
Still wonder how much salt it would take to kill them?

[Deleted]

Feb 11, 2014 20:28:29 GMT -5 BentRod said:

I can't seem to download your file.  Here is a picture of the 2013 data I was given.  To get a clearer picture, I mapped out the various ages and included the max and min when meaningful. All the other numbers are simply the average for that age.  I had to do this because I don't have the raw data. As shown, the sample size is 132 which is great.  However, the number of fish > 30 inch is 9 which accounts for 7% of this data.  Additionally, in 2013, 10% of the fish were age 9 or older.  In 2012 and 2011, 25% and 28% of the sample was age 9 or older, respectively.



If this 2013 data is correct, then we are fishing a lake that is similar to 05-06 in terms of the number of 30+ fish as shown in the next picture. 



Note: I do not have the 2013 fishermen data. The above table is the 2013 sample data compared to the fisherman data from the past. The 2011 and 2012 sample data was pretty close to fisherman data in terms of probability. Thus, if the 2013 fisherman data shows a drop like the sample data, I would be greatly concerned. However, my premise is that since I am new to SML and my own personal data is more like the fisherman data from the past, then the 2013 sample data is wrong.  I caught more 30+ fish in my 4 trips than what is shown in the 2013 sample data.

So...Bentrod... is this the right data???  I am not sure if I want to know the answer!  

[Deleted]

I just downloaded your file.  It is exactly what I have. I am not sure how you see a bunch of 30+ fish in the 6-8 age range.  I can only make out 3. Of course there are probably several more in the raw data. What concerns me more is the % of age 9 and over.

[Deleted]

I hadn't planed on commenting in this thread further, figured everything that could be said,  had been..... yam, just so you know you are not crazy....this is a pm I sent earlier today to a fellow member......


You and I both know that insufficient data leads to many different conclusions and/or can serve many different purposes, whether there be outside influence, funding, or heck even the fear of losing ones job from past mistakes. Now, do I think dan is cherry picking his data, absolutely not. I just feel that dans data is skeewed to much from the summer time fishhead data, (when the fish are really stressed and are at their lightest weight, and more than likely losing weight) and not enough bigger fish data. Granted, I didn't fish as much in 2013 as I usually do, fished 45 days and 39 of those were half day trips but i'm with yam, my numbers don't add up to dans. Either i'm the luckiest SOB to ever fish SML or something is wrong with the data. Even with my somewhat limited time on the water, we caught a very, very good # of 30 to 35 inch fish in 2013. Were those fish 7 or 10 years old, I don't know, but they certainly looked healthy.I would never kill a bigger fish to send dan a fish head, nor would you or any of the other serious fishermen on here. So his data can't be right. Is it his fault.... no...he is trying to work with what limited data he has...... example, in december, I had to fillet a 16lb fish that the hook slid down thru her gill....she had 15 three inch ales in her gut and still eating and packing on weight....what do you suppose she weighed in august...i'm "guessing" no more than 13 lbs. A 3 lb. wieght gain in 4 short months would be  pretty awesome.

Are there to many small fish in the lake, I don't know, but there certainly is alot.......the fishing pressure isn't going to go away on the lake. If we seriously deplete the the samaller fish population (which is what will happen) all the meat chasers will be forced to fish for bigger fish and you know what that will do......Don't get me wrong, I love catching big fish and would like to see them raise the slot on the higher end. Rasing it on the lower end really, really make me nervous.......I've been through 1 catastrophe on the lake and don't want to go thru another.....

Is there an answer ......i'm not 100% sure there is a problem.

[smythley]

The tough part about wildlife /fisheries research is that there is a lot going on. You've got unequal sample sizes, unequal sampling effort, high variation, a population that you cannot get a census of, environmental factors, critters that move and change (unlike a pine tree that stays in one spot, or a piece of steel, that doesn't change much), complex relationships with other organisms, and probably hundreds of other variables that we can't see or understand, much less measure. Do stats always fit neatly? Is your R square value always close to one?
I can cruise a stand of timber and do some coring, and with enough points and samples, give you a dern good idea of a diameter to age relationship, with a pretty linear regression with a high R square. Heck, you want high enough precision, and have enough funding, and I'll measure every tree on the place.
Critters ain't that easy. Yeah, biologists look at trend data. They have to. It's one tool in their rolling Craftsman box.
How bout anecdotal data? A good example is the whole bait/forage issue...talk around the campfire is that there is tons of bait. What exactly does this mean? Does this mean that the guys on the lake that are great at finding bait catch it every time they throw the net? Does it mean that I can go banana throw my 8 footer off any dock at any time and catch 87.5 gizzards?
Anyway, more data is always better...one reason I think everyone should have an angler diary and keep good records. More data won't necessarily answer all the questions, but may help make it slightly clearer.
Anyway, sorry to ramble. Great to see folks that are passionate about the fishery. We may not all see eye to eye, but the dialogue is good. Tight lines guys...

[mwardncsu]

I'm not debating a potential summer-time bias to the fish head collection - though it's not all just summertime. Let me see if I can find out the date distribution across the year across the years.

Maybe there is some confusion on the head data for ages. It is not saying we didn't catch lots of 30"+ fish - it's just saying that N fish head of that size were submitted from which the age was determined. Knowing many of the guys that typically contributed fish heads - they have a bias to not keep them except in the summer (if then) - so the collected data is lower - which, yes, affects it's overall margin of error.

Also - on 2013 - the data set Tyler attached was what was reviewed in the summer timeframe - so most heads collected in the summer were not yet processed. Just something to highlight - assuming the other years were generally representative the data set from 2013 is not complete - if it matters.....

The key discussion point to which the hypothesis was formed is not the number of fish over 30" - it is if our fish are growing at the right rate as they get into the mid-20" range. Though I will acknowledge that having more data from larger fish help to have a better curve.


Through all of this I'm reminded of a few sayings....


"Facts are stubborn things, but statistics are pliable." - Mark Twain

"99 percent of all statistics only tell 49 percent of the story." - Ron DeLegge

"Statistics were magic like this: they could tell you with near-certainty that a thing would occur, without a hint of when or where." - Hugh Howey

"If your experiment needs a statistician, you need a better experiment." - Ernest Rutherford

"There are three types of lies - Lies, Damn Lies, and Statistics" - Benjamin Disraeli